RPM / Speed / Gear Questions

Hello everyone,

I have come to the understanding that the XJs like to rev a bit higher, and I am trying to get that into my head when riding. I had been playing it 'safe', maxing out the gears at about 3-4k, reaching 5th gear at about 45mph but lately I have have been going closer to 5k and up...I'm definitely not used to such high RPMs so I guess I have a bit of fear in the back of my mind when riding.

My question is what speeds do you usually hit in which gears. I myself have an 81 XJ650 so hearing responses from members with similar rides would prove helpful.

Thanks

 

If you're shifting at 4K you haven't even tapped the "fun zone."

These motors don't begin making serious HP until 6K rpm. REV IT. (Assuming it's in a proper state of tune.)

 

Properly tuned, these bikes wake up north of 7K. If you're keeping it that low you're missing out.

Where you shift depends on how quick you want to get away from where you just were.

Just cruising around I'll shift whenever without paying much attention. Need to get up a ramp, twist it open and let it scream. Shift around 8 or 9k. But hang on the beast is awake at that RPM.

 

It all depends on my mood - mostly I'll change as low as you have been and pooter about, but on the odd occasions I get out of town I can use the revs much more. As has been said, the XJs come alive after 6K.

 

For me:

2nd - 20mph
3rd - 35-40mph
4th - 50-60mph
5th - I only use 5th at motorway speeds, or if I'm cruising down a back road for miles, to save fuel.

When I want to "get after it" I'll take 2nd up to 7,000rpm, then I have to back off because I'm going about 5mph over the limit.

Most places in the US you can't redline 2nd gear because you'd be speeding.
(although it is FUN to do :twisted: )

 

All this is very good to know. I just have to get over my little stigma of seeing the RPMs that high. What should the engine sound like at 6-7k?

Another question, how does putting the revs that high affect all of your mileage?

 

Revs vs mileage is a two-way street.

Will it use more fuel at 8,000rpm vs 5,000rpm? yes, of course it will.

BUT

If you shift at 3,000rpm all the time, you are actually making the motor work harder, and probably not burning all of the fuel the motor is taking in. So you could be using more fuel at 3,000rpm than at 5500rpm.

Also, keep in mind, your charging system doesn't kick in until around 2,000rpm, so if you are always shifting between 2K and 3K, you are actually hurting your battery a bit.

 

That is great info tskaz!

I have my shims in spec, and I definitely hear a slight "chatter" of the valves when running which I understand is normal. How normal is a "whirring" or higher pitched rev sound? I did a vacuum sync, which I want to do again just to be sure and to dial in the idle. I still need to do mixtures also, but I am waiting for my Colortune. Anything else I should do to make sure my engine is properly tuned for higher revs?

 

Check your plugs for color once in a while. Lunch bag brown is the goal.

I remember getting my bike on the road for the first time after I got it and each spring when it's been awhile since I've ridden it. Takes me a bit too to let the RPM up. I guess that comes from driving a jeep and a diesel pickup. Both would probably throw rods at 4 or 5k.

 

And clean plugs in-between checks to have a "blank canvas"?

 

I haven't found that necessary. They'll change colors on their own. If they are black black maybe make some adjustments and toss a new set in. About $8.

 

Thanks everyone. The more I work on this bike, the more I find it was the best investment I've probably ever made. The knowledge I'm getting working on it and from all the help on this site is well, well worth the price of admission. Not to mention, I love my bike!

 

3-4k is alright for pootling around, but not for acceleration. Go higher and you'll find a big hole at 6k. Work round this by spinning up to 8k in the lower gears if you want to get a move on. It does feel high for an older bike but it's the way Yamaha designed it.

 

Hi. I have XJ650J- my mileage on the last tank was 47 mpg, I have been tending to run at higher rpm's this year because it's fun and has begun to feel "normal". Last year I regularly saw 52-53mpg but I wasn't rpm'ing as highl.
You will probably feel a range where there is some noticeable vibration - around 4900-5000 rpms, I think. That is common on these bikes due to engine/drivetrain harmonics. It is less harsh if the valves/carbs are all set correctly. It goes away above 5200rpm and on mine, it's real smooth at 5500+. My bike is happier at 60mph in 4th than it is in 5th and can run all day like that! Same with 75mph at 6000 rpm in 5th gear- it feels smooth and like it could do it all day. all day. However, if I'm doing 55 for an extended time, 5th gear is great on gas at that speed/rpm and it's just below the 'vibration zone'.

 

Another consideration is oil movement. Your pump is more efficient at higher rpms and moves more oil at a faster pace. With the airheads this is important because the engine is basically relying on the air in the fins and oil moving to stay cool.

Having owned a Honda CB650 (hydraulic valves) and after riding many water cooled bikes, it took me a while to get used to the XJ 'sound'. These engines contain nothing 'extra' and as a result they seem noisy by comparison. You should hear your valves tapping at idle and while revving up you should hear a nice eager growl. And as said when in tune revving up is fine-from experience my 550 would rather run above the harmonic level (3.5k to 5k) most of the time. Going for gas mileage I will go to 6th around 55. Of course above 8k it positively sounds like it's a speed obsessed beast, and rides like one too! The Honda was more tame (soundwise) at the same rpms.

 

These motors absolutely scream. They are noisy at idle and should be. Valve tapping is normal. Load metallic knocking is not. When reved, it will raise the eyebrow of any modern sportbike owner. One not familiar with XJ's will swear the thing is about to fly apart, but it is a rock solid plant if well maintained. In the happy range of the rpm's, it had a sweet low mellow tone unlike sportbikes which are more high pitched.

 

Yea!!! These bikes are fun. Mine actually raises the hair on the back of my neck when I hit the 7K mark up. That and the back wheel acts like your hotrod car does when you step in it (Rear tires start drifting to the side) That is how mine feels at that RPM only with a single tire.... Gotta Love-Um

 

i've been out of town for 5 days now and won't be back to my bike for another 5. After reading through this thread, i've never missed my bike more. I can't wait to ride it and feel the thrill again!

question, though. i don't know if my tach is the original, and I don't have mine around right now, so i don't remember where the redline is, but what do you fellas feel about about putting it close to the redline? It really takes no time at all for my seca to go from 6000 all the way up. i get nervous about being too hard on it and back it off. do you guys keep it in the redline region much?

 

I run my 550s into the red all the time. (10K on the 550.)

Just be sure your valves are in spec and you aren't running lean, then let it run!

 

Redline? What redline? I can't find one anywhere on my Tach!

Ha! Seriously the only way I can tell if I'm near is the power drop, but even then the engine still sounds pretty happy. It seems to enjoy 10 grand as much as I do.